Reveksible gear pump



.Jarl- 21, 1964 A. M. ALDRlcH 3,118,387

REVERSIBLE GEAR PUMP Filed March 15,. 1962 w @da United States Patent O "ice 3,113,387 REVERSEBLE GEAR PUMP Alvin Aldrich, Marlboro, lviass., assigner to W. H.. Nichols Company, Waltham, Mass., a corporation o hdassachusetts Filed Mar. 13, 1.962, Ser. No. 179,303 2 Qlairns. (El. 103-117) This invention relates to a gear pump which is reliably reversible so that it pumps fluid in a single direction regardless of which way its drive shaft is rotated.

The invention relates more spem'lfi'cally to a pump of the Gerotor type which operates on the principle of that illustrated for example in Patent No. 2,140,966, granted December 20, 1938, to Arthur A. Nichols. Pumps of this type have been employed to pump a uid in a single direction no matter which direction the pump was operated, but lthey have been unreliable in operation. According to the present invention, reliability is assured.

For la more complete understanding of the invention, reference may be had to the following description thereof, and to the drawing, of which FIGURE 1 is a sideV elevation of a pump embodying the invention, a portion being broken away to show in section;

FIGURE 2 is a section on the line 2 2 of FIGURE l;

FIGURE 3 is a section on the same line, but showing the parts in a `dilerent position of operation; and

'FGURES 4 and 5 are magnified fragmentary sectional views of a detail in different positions of operation.

The mechanism shown comprises a driven shaft 10 on which is mounted an inner wheel or rotor 12 for rotation therewith. The inner rotor l2 has any desired number of gear teeth '14 with spaces 16 between, four such teeth being shown. Surrounding the inner rotor and eccentric thereto is an outer wheel or rotor Z having inner teeth 22 with spaces 24 between. The number of the teeth Z2 is one greater than the number of the teeth T4. The outer rotor Z0 is fitted within a split ring 30 the outer periphery of which is concentric with the shaft 10, the inner periphery being eccentric thereto. This ring can rotate within a stationary casing 62 between the two positions shown in FIGURES 2 and 3, respectively.

A supply pipe 34 for uids communicates through an inlet opening 36 with the chamber in which the rotors 12, 2o are located. A discharge pipe 3S communicates with that chamber through an outlet opening 40 located on the other side of the sharft from the inlet opening 363. When the rotors 1.2, are rotating in the counter-clockwise direction and the ring 30 is in the position shown in FIGURE 2, the space between the portions of the inner and outer rotors passing the opening 36 is expanding and is thus drawing fluid in through that opening. At the same time, the space between the portions of the rotors passing the opening 40 is contracting and is thus forcing the liuid therein through that opening and into the discharge pipe 38.

When the rotors 12, 2.0 are rotating in the clockwise direction and the ring 30 is in the position shown in Patented dan. 2l, l'l

2 FIGURE 3, the Iiiuid is in like manner drawn in through the opening 36 and forced out through the opening 40. Hence, if the fit? always turns when the direction of rotation of the rotors change-s, the direction of fluid discharge will always be in the same direction regardless of which way the shaft 10 is turning.

To ensure prompt reversal of position of the ring 30 when the rotation of the shaft reverses, the ning is made with an unstressed inner diameter slightly less than the diameter oi the outer rotor 20 so that when it surrounds the rotor 20 it normally -grips it and turns with it. During the operation of the pump, however, the rotor 20 must turn freely within the ring. Hence a cam lever 50 is arranged in a gap '52 between the split ends orf the ring to cam the ends away from each other when the lever is rocked and thereby to loosen the grip of the ring 0n the rotor Z0. To rock the lever 5d at the proper places, two stop pins 54, 56 `are mounted in the groove 5S within the casing 32 in which moves the outer end of the lever 50 when the ring 30 turns. When the direction of rotation of the rotors -is counterclockwise, the ring 30 is carried around in the same direction until the outer portion of the `cam lever 5d strikes the pin '54 and is rocked thereby as shown in FlGURES 2 and 4. This earns the ends of the split ring apart and releases its grip on the outer rotor Ztl, a clearance et) between the ring and outer rotor being indicated in FIGURE 4.

lf the rotation of the shaft and rotors changes to clockwise, the lever S0 moves away from the pin 54 and takes a neutral position as illustrated in FIGURE 5. The ring 30 thus grips the rotor 20' and is carried thereby until the lever strikes the pin 56 and is rocked thereby to release the rotor 20 as indicated in FIGURE 3. Each reversal of rotation of the Shaft and rotors thus results reliably in an immediate reversal of the position of the ring 30.

I claim: e

1. A gear pump comprising :a casing, a split ring rotatable within said leasing, said ring having an inner periphery eccentric with respect to its outer periphery, an outer rotor fitted within said ring and adapted to be gripped thereby, said outer rotor having 4a series of inward gear teeth, an inner rotor having outward gear teeth one less in number than the teeth of the outer rotor, said inner rotor being con-centric with the outer periphery of said ring, a rotatable shaft on which said inner rotor is mounted, said casing having ports communicating respectively with spaces between said rotors on Iopposite sides of the axis of said shaft, and means operating to cam the ends of said split ring apart so as to release its grip on said outer rotor when said ring has rotated to either of two angular positions approximately 180 apart.

2. A pump as described in claim l, said camming means comprising a lever rockably arranged between the ends of the spl-it ring, #and two fixed pins alternately engageable by said lever to rock the lever.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A GEAR PUMP COMPRISING A CASING, A SPLIT RING ROTATABLE WITHIN SAID CASING, SAID RING HAVING AN INNER PERIPHERY ECCENTRIC WITH RESPECT TO ITS OUTER PERIPHERY, AN OUTER ROTOR FITTED WITHIN SAID RING AND ADAPTED TO BE GRIPPED THEREBY, SAID OUTER ROTOR HAVING A SERIES OF INWARD GEAR TEETH, AN INNER ROTOR HAVING OUTWARD GEAR TEETH ONE LESS IN NUMBER THAN THE TEETH OF THE OUTER ROTOR, SAID INNER ROTOR BEING CONCENTRIC WITH THE OUTER PERIPHERY OF SAID RING, A ROTATABLE SHAFT ON WHICH SAID INNER ROTOR IS MOUNTED, SAID CASING HAVING PORTS COMMUNICATING RESPECTIVELY WITH SPACES BETWEEN SAID ROTORS ON OPPOSITE SIDES OF THE AXIS OF SAID SHAFT, AND MEANS OPERATING TO CAM THE ENDS OF SAID SPLIT RING APART SO AS TO RELEASE ITS GRIP ON SAID OUTER ROTOR WHEN SAID RING HAS ROTATED TO EITHER OF TWO ANGULAR POSITIONS APPROXIMATELY 180* APART. 